A side airbag apparatus is disclosed in JP-A-2003-237519, wherein a folded airbag is accommodated within a seat back and caused to expand between a vehicle occupant and a side part of a vehicle body to protect the vehicle occupant when a side part of the vehicle receives an impact.
In the side airbag apparatus, three dividing walls are formed in an airbag, and three flow channels are formed by the dividing walls in the airbag.
The three flow channels are thus formed in the airbag. When gas is discharged from an inflator, the flow of the discharged gas is controlled by the flow channels, whereby the gas is efficiently guided throughout the entire body of the airbag, and the entire body of the airbag is caused to expand quickly.
In the conventional airbag thus arranged, the entire body of the airbag is quickly expanded. The expansion is therefore not performed in accordance with the importance of any particular body part of the vehicle occupant. For this reason, airbags have scope for improvement to allow better protection to the vehicle occupant.
It should also be noted that in order for airbags to expand quickly, a relatively large amount of gas should be filled into the airbags. This requires associated inflators to discharge a relatively large amount of gas, thus presenting a bar to the downsizing of such inflators.
More specifically, for appropriately protecting a vehicle occupant, excessive filling of gas into an airbag must be avoided. For this reason, airbags usually have a vent hole for discharging gas upon deployment of the airbags. Such a vent hole also releases gas while the airbags are being deployed. This requires the inflators to discharge a relatively large amount of gas. This makes it difficult to downsize the inflators.